The most fascinating thing about rocks and minerals is that they tell us something about our past. Rocks and minerals record the environment in which they formed, which tells us something about the evolution of the Solar System, the evolution of Earth, and ultimately, the evolution of life here on Earth.
A Record of Past Geological Environments and Processes
All rocks and minerals form under certain chemical and physical conditions. As we find rocks and minerals, we know that in order for these certain types to have formed, particular chemical and physical conditions must have existed in the area. Rocks and minerals can give us information about:
- past climates
- dryer climates
- wetter climates
- geologic activity
- mountain building
- volcanic eruptions
- fault movement
- meteorite impacts
- evolution and extinction of species
For example, where igneous rocks and minerals are present, there was likely a volcanic eruption, or perhaps some plate rifting that caused magma to come to the surface. Where sedimentary rocks and minerals are present, there were likely some lakes or rivers that eroded and re-deposited the sediment. Where metamorphic rocks and minerals are present, there was likely fault movement or crustal deformation like that in mountain building. Rocks containing fossils also tell us about the evolution and extinction of species and in what kind of environments these species thrived or struggled.
Some rocks and minerals undergo numerous changes, telling a story that spans billions of years. In Western Australia's Jack Hills rock formation, a tiny zircon mineral grain tells scientists a story about the evolution of Earth. According to geochemical analysis, and the type of metamorphic rock in which the mineral was found, the mineral must have formed as part of the earliest granitic crust on Earth; but most importantly, also in the presence of water. The mineral grain has been dated to be 4.3 to 4.4 billion years old, so this means that continental crust and water here on Earth existed far earlier than previously suggested.
Petrology and Minerology of the Solar System
Knowing what kinds of environments must exist here on Earth to produce certain types of rocks and minerals also tells us something about the petrologly and mineralogy of other planets and moons in our Solar System. For example, using remote-sensing techniques, planetary geologists have found phyllosilicates on Mars. Phyllosilicates are a type of mineral that are related to clay and form in wet conditions here on Earth. Therefore, in order for phyllosilicates to exist on Mars, liquid water must have existed on the surface of Mars at some point in its planetary evolution.
As we discover more rocks and minerals on Mars, and other Solar System bodies, and understand what kinds of conditions need to have existed in order for them to form, we better understand the evolution of the Solar System. Key finding of minerals that give us information about the presence of liquid water also provide clues as to whether or not life may have existed on other bodies in our Solar System.
Sources:
"Earth's Oldest Mineral Grains Suggest an Early Start for Life", NASA.gov
"New Clues Suggest Wet Era on Early Mars was Global", jhuapl.edu
Related Articles:
Alexandra Matiella Novak - With a PhD in Geology and expertise in science education, Alexandra is passionate about increasing the public's Earth science literacy.
